Electrical connector



Oct. 9, 1962 s. SCHNEIDER ELECTRICAL CONNECTOR Filed Jan. 29, 1960INVENTOR. STANLEY SCHNEIDER United States Patent Ofifice 3,058,083Patented Oct. 9, 1962 3,058,083 ELECTRICAL CONNECTOR Stanley Schneider,Newtown Square, Pa., assignor to Burroughs Corporation, Detroit, Mich.,a corporation of Michigan Filed Jan. 29, 1960, Ser. No. 5,503 4 Claims.(Cl. 339-17) The invention hereinafter described and claimed has to dowith separable electrical connectors and more particularly to separableconnectors of the socket type primarily useful in interconnectingelectrical components or circuitry.

A problem with the use of electrical and electronic assemblies andsub-assemblies is the lack of reliability of the interconnection betweencomponents forming the sub-assemblies and even between thesub-assemblies themselves. Many of such interconnections are of thenon-separable or permanently connected type and these are fairlyreliable. However, we are concerned here with the pressure contact typewhere electrically conductive interconnections are by pressure of oneconnector against another. Plug-in connectors are a common example ofthis type of interconnector and for the most part such connectorsusually rely upon only one, but rarely more than two, points of contactfor such interconnection. Good overall properties in separableconnections are diflicult to achieve because of the compromise neededbetween good contact usually requiring high contact force, and ease ofremoval better effected with low contact force.

The usual spring type connectors wherein a terminal pin is inserted orplugged axially into the spring whereby the coils of the spring areforced to expand and grip the pin circumferentially, can provideadequate contact pressure but the area of contact is so extensive as tocause the spring to act like a Chinese finger when an attempt is made towithdraw the pin from the spring to separate the connection-4e, theharder the pull to separate them the tighter the spring tends to hold onto the pin. Such separating attempts often result in the destruction ofthe spring connector.

Therefore, it is an important object of the present invention to providea separable electrical connector overcoming the above-mentioneddifiiculties by a construction capable of effecting interconnection ofelectrically conductive terminal elements with a high degree ofreliability.

Another important object of the invention is to provide a spring typeseparable connector readily adapted for manufacture in micro-miniaturesize for use in miniaturized circuit assemblies.

More specifically it is an object of the present invention to provide aninexpensive spring type separable electrical connector providingmultiple contact points of low area and high contact force providing foreasy insertion and withdrawal of associated pin connectors, and aconnector which is characterized by its ease of assembly with associatedapparatus.

In accordance with the above object and first briefly described, theinvention comprises a socket type coiled wire spring connector for usewith a pin type terminal connector and wherein the coil is so formed asto have a major transverse dimension through the axis of the coilgreater than the diameter of the mating pin connector and a minortransverse dimension through the axis of the coil less than the diameterof said pin connector, whereby upon insertion of the pin connector intothe spring connector the coils of the spring are urged into multiplepoint contact with the pin connector on opposite sides thereof acrossthe minor transverse dimension and with maximum force. The spring coilterminates in an extension by which it is easily attached to the socketbase or other associated apparatus.

In the accompanying drawings illustrating the preferred embodiment ofthe invention:

FIG. 1 is a general perspective view of a miniaturized electronic moduleof triangular shape plugged into a printed circuit panel containing aplurality of transverse rows of spring connectors in accordance with thepresent invention, the connectors being positioned in apertures formedin the upper surface of the panel thus to form the socket connector;

FIG. 2 is a fragmentary plan view of one of the apertures shown on thepanel of FIG. 1, and showing a pin type connector plugged into a springconnector in accordance with the present invention;

FIG. 3 is a sectional view taken on the line 3--3 of FIG. 2 but showingboth connectors in elevation;

FIG. 4 is a plan view of a coiled spring connector in accordance withthe present invention but in a condition intermediate to its finishedform;

FIG. 5 is an elevational view of the spring shown in FIG. 4;

FIG. 6 is a plan View of a spring type connector in accordance with thepresent invention and showing its elliptical shape;

FIG. 7 is a side elevational view of the connector as shown in FIG. 6;and 7 FIG. 8 is a view similar to FIG. 3, but showing a modified form ofthe connector.

Now more specifically with reference to the details of the drawings andfirst to FIG. 1, there is shown an electronic miniaturized electricalmodule 10 mounted on a printed circuit panel 11. The construction shownin this figure is in accordance with the invention described and claimedin the copending application of Edgar O. Sprude, Serial No. 860,602,filed December 18, 1959, entitled Modularized Electrical NetworkAssembly and assigned to the assignee of the present invention.

According to the Sprude application, the panel 11 is provided on itsupper surface, as seen in FIG. 1, with transverse rows of apertures orrecesses 12 each of which, as seen in FIGS. 2 and 3, is provided with asocket type separable electrical connector 13 for receiving terminal pinconnectors 14 projecting from the lower edge 15 of the module it),normally, but not necessarily, having a pin connector for each of theapertures 12 in a row. The lower surface 16 of the panel 11 is providedwith printed circuitry 17 in accordance with a predetermined pattern toestablish the desired circuits.

In accordance with the present invention, each of the connectors 13within the apertures 12 comprises a coiled wire spring portion 18including a plurality of convolutions, and an axial portion or extension19. The coiled portion 18 is formed by wrapping wire around a circularmandril or rod in the manner usually used for forming a coil spring, asseen in FIGS. 4 and 5, and in a manner resulting in the inner diameterof the loops or convolutions of the coil being greater than the diameterof the pin connector 14.

In one actual embodiment of the invention for use in a miniaturizedmodular network assembly, the pins 14 have a diameter of .020". Thecoiled portion 18 of the connector 13 is wrapped about a mandril of thesame diameter, but when removed from the mandril the coils spring backto a larger dimension in the neighborhood of .025" substantially asshown in FIG. 4. In this condition the diameter of the coiled portion isuniform throughout its length about the axis 20, as seen in FIG. 5. Bysuitable means, not shown, the coils or loops 21 of the spring are thensimultaneously rotated about axes perpendicular to the axis 20 andrelative thereto to a new set condition (FIGS. 6 and 7). Such rotationmay easily be accomplished by holding the coils along one side the left,as seen in FIG. 7and urging the other sidethe right, in FIG. 7-upwardly,as shown by the broken and full line showing of loop 21a in FIG. 7, thusto decrease the angularity of the planes of the loops relative to theaxis 20 to a degree decreasing the transverse dimension 22, of theaperture through the coil, see FIG. 6, to a dimension something lessthan the diameter of the pin 13 (.020). It will be understood, ofcourse, that the diameter of the individual loops is not materiallychanged from its original dimension, and that when looking in thedirection of the arrow 23, at the top of FIG. 7, each loop will appearas a circle rather than an ellipse. However, when looking directly downupon the coils along the axis 20, as seen in FIG. 6, in the direction inwhich the pin 14 will be inserted, it will be seen that the coiledstructure is now of elliptical shape and that each loop 21 has peakedportions at the ends of the major axis of the ellipse.

When a pin 14 is inserted axially in the coiled portion 18 of theconnector, the individual loops of the spring 20 are rotated by the pintoward their original condition (FIGS. 4 and sufiiciently to accommodatethe pin therebetween (FIG. 2) and will grip the pin at points onopposite sides thereof, as indicated at 24, with sufficient pressure toinsure good electrical contact of the connector with the pin and at aplurality of points corersponding to the number of loop points 24 incontact with the pin. It will also be understood that as the pin 14 isinserted in the coiled portion 18 of the connector, the points 24 willbe in wiping contact, thus to assure good electrical conductivitybetween the pin 14 and the connector 13. With a wire of .006" dia. andthe dimensions mentioned above, a contact pressure up to 4 02. isobtainable.

Insertion and withdrawal of the pin from the coil 18 is relatively easybecause of the low area of contact therebetween at points 24 and becausethe convolutions of the coil have not been stressed or stretched byinsertion of the pin. The only pressure is exerted by the desire of theconvolutions of the coil to return to their set condition shown in FIGS.6 and 7.

Now with reference to FIG. 3, it will be seen that the axial extension19 of the connector projects through a small axially positioned hole 25through the bottom Wall of the aperture 12 and is formed with a loop 26turned into engagement with the printed circuitry 17 on the underside ofthe panel 11. The loop is formed by a suitable tool after the extension19 is passed through the aperture 22, which will be While the extensionis in the shape shown in FIG. 7. Preferably the connector 13, as seen inFIG. 7, is inserted into the aperture 12 until the left side 21]) of thelowermost coil 21:! contacts the bottom of the aperture after which theextension 19now extending straight through small aperture 25is formedinto the loop 26 so that the distance between its inner edge 27 and thelowermost portion 21b of the lower loop 21:: is less than the distancebetween the outer surface of the printed circuit 17 and where the bottomedge 21!) of the loop 21a is in contact with the bottom of aperture 12,whereby a spring force urges the loop 26 at point 27 into tight contactwith the printed circuit 17.

From the above description it will be understood that this novelconnector construction lends itself well to dip soldering techniqueswhereby, if desired, the loop 27 may be soldered into contact with theprinted wiring 17 and, furthermore, the loop 26 provides means forconnecting a test probe to test the circuitry within the module after itis plugged into the panel 11.

It will be realized, of course, that the connector may take other formswithin the scope of the invention, one such form being illustrated inFIG. 8 where the extension 19 is tangent to the coils of the connectorand extends through a small hole a through the panel 11 offset 4 fromthe axis of the aperture 12 rather than axially as shown in FIG. 3,illustrating the preferred form.

It will be understood too that the angularity of the coils of theconnector to the axis 20, as shown in FIG. 7, may be varied inaccordance with the diameter of the pin 14, which is to be inserted inthe connector. It will also be understood that by the use of a suitablemandril or other tool that the coils of the connector may be woundoriginally in the desired angular relationship one with another, as seenin FIGS. 6 and 7, thus eliminating the necessity of rotating the coilsas described above.

What is claimed is:

1. In a socket-type connector for effecting separable electricalconnection with a terminal pin, wherein a terminal board of dielectricmaterial is provided with a recess in one surface, a hole of smallerdimension than said recess extending through said board from the bottomof said recess to the other surface of said board, and an electricalconductor bonded to said other surface: a coiled wire electricallyconductive spring connector positioned within said recess with one openend exposed to said one surface for the axial insertion therein of theterminal pin, said spring connector comprising, a plurality of helicalloops of the same diameter arranged along a common axis with the axis ofeach loop angularly related to said common axis to an extent whereby theloops cooperate to form an elliptical structure around said common axiswith a minor inside dimension across the common axis of said ellipseless than the diameter of said terminal pin and a major inside dimensionacross said common axis of said ellipse greater than the diameter ofsaid terminal pin, whereby said terminal pin when axially inserted intosaid spring connector will contact the helical loops only at pointsspaced across the minor inside dimension, and a terminal end extendingfrom the other end of said spring connector in one direction throughsaid hole and in another direction into contact with said electricalconductor at a point removed from said hole, in such manner as toresiliently secure said spring connector against the bottom of saidrecess and so position it that said common axis will be substantiallynormal to said terminal board.

2. In a socket type connector for effecting separable electricalconnection with a terminal pin, wherein a terminal board of dielectricmaterial is provided with a re cess in one surface, a hole of smallerdimension than said recess extending through said board from the bottomof said recess to the other surface of said board, and a printed circuitconductor on said other surface: a coiled wire electrically conductivespring connector positioned within said recess with one open end exposedto said one surface for the axial insertion therein of the terminal pin,said spring connector comprising, a plurality of helical loops of thesame diameter arranged along a common axis with the axis of each loopangularly related to said common axis to an extent whereby the loopscooperate to form an elliptical structure around said common axis with aminor inside dimension across the common axis of said ellipse less thanthe diameter of said terminal pin and a major inside dimension acrosssaid common axis of said ellipse greater than the diameter of saidterminal pin, whereby said terminal pin when axially inserted withinsaid spring connector through said open end will contact the helicalloops only at points spaced across the minor inside dimension, and aportion extending from the other end of said spring connector throughsaid hole and terminating in a resilient loop pressing against saidprinted circuit conductor and said printed circuit conductor in turnpressing against said other surface thus resiliently urging said springconnector into said recess against its bottom wall, and securing saidspring connector to said terminal board in such manner that said commonaxis will be substantially normal to said terminal board.

3. A socket type separable electrical connector comprising: a printedcircuit panel having wiring printed on at least one surface thereof anda circular recess in the opposite surface; and a coiled Wire springconnector coaxially positioned within said recess, each of the coils ofsaid spring connector being formed by peaks progressively spaced aroundand substantially equally spaced from the axis of said spring connector,and portions interconnecting said peaks, the latter interconnectingportions having mid-portions cooperating to form an axial aperturethrough said spring connector with a minimum transverse dimensionthrough said axis less than the diameter of a pin connector to bereceived therein, whereby said pin connector when inserted axiallyWithin said spring connector may be in point contact with themid-portions of said interconnecting portions; said circular recess insaid panel having its axis normal to the panel surfaces, a diameterslightly larger than the major transverse dimension through the axis ofsaid spring connector, and an aperture extending through its bottom wallto the said one surface with the diameter of said aperture less than thediameter of the recess and less than the major transverse dimensionthrough the axis of said spring connector; said spring connector alsohaving a portion extending through the aperture in the bottom wall ofsaid recess and terminating in a spring loop in contact with saidprinted wiring in a manner biasing the bottom of said spring connectortightly against the bottom wall within said recess thus to lock saidspring connector to said panel in electrically conductive relation withsaid printed wiring.

4. In a socket type separable electrical connector wherein a printedcircuit panel has Wiring printed on at least one surface thereof and acircular recess in the opposite surface: a coiled wire spring connectorsubstantially coaXially positioned within said recess, each of the coilsof said spring connector being formed by peaks progressively spacedaround and substantially equally spaced from the axis of said springconnector, and portions interconnecting said peaks, the latterinterconnecting portions having mid-portions cooperating to form anaxial aperture through said spring connector with a minimum transversedimension through said axis less than the diameter of a pin connector tobe received therein, whereby said pin connector when inserted axiallywithin said spring connector will be in point contact with themid-portions of said interconnecting portions; said circular recess insaid panel having a diameter slightly larger than the major transversedimension through the axis of said spring connector, and an apertureextending through its bottom wall to the said one surface with thediameter of said aperture less than the diameter of the recess and lessthan the major transverse dimension through the axis of said springconnector; said spring connector also having an end portion extendingthrough the aperture in the bottom wall of said recess and terminatingin a spring loop in contact with said printed wiring in a manner biasingthe bottom of said spring connector tightly against the bottom wall ofsaid recess thus to lock said spring connector to said panel inelectrically conductive relation with said printed wiring.

References Cited in the file of this patent UNITED STATES PATENTS889,812 Russell June 2, 1908 1,619,699 Broad Mar. 1, 1927 1,933,304 BellOct. 31, 1933 2,803,000 Johanson Aug. 13, 1957 2,882,514 Krantz Apr. 14,1959 2,902,629 Little et al. Sept. 1, 1959 2,942,332 Wright et al. June28, 1960 2,982,935 Barnard May 2, 1961 3,013,245 Osborne Dec. 12, 1961FOREIGN PATENTS 208,043 Australia May 14, 1957 493,859 Italy May 10,1954 1,013,561 France Apr. 30, 1952

